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Re: [TowerTalk] Coax Losses on 160 and 75?

Subject: Re: [TowerTalk] Coax Losses on 160 and 75?
From: Jim Brown <>
Date: Fri, 5 Aug 2016 23:24:17 -0700
List-post: <">>
On Fri,8/5/2016 11:03 PM, Richard (Rick) Karlquist wrote:
No, this isn't the real deal.  A 2 port vector network analyzer
with full 2 port calibration is the real deal.  The wattmeter
approach has many error effects that are difficult to account

Right. I've never considered using wattmeter(s) to measure loss in coax. Now I use a DG8SAQ-designed VNWA (vector network analyzer). Very good accuracy.

Before that, I used an HP generator as a source and an HP Spectrum Analyzer as an RF voltmeter. Using that for measurement, I could clearly see variation in the apparent loss below 2 MHz -- this was as a result of the mismatch between this coax (Zo of a real line is complex and varies with frequency) and the constant 50 ohm load and source terminations. BTW -- I was measuring a sample about 1,200 ft long.

73, Jim K9YC


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